grommunio Alternatives

Secure Email Gateway

Fortinet Email security is designed to block ransomware, phishing, and other cyber threats seeking entry via incoming email and outgoing messages don’t improperly leak sensitive data.

The #1 email warming service to improve your deliverability by generating realistic and meaningful engagement to your emails. Easy-to-use solution to help you land in the main inbox instead of the spam folder.

Visit website paid $19.5 / Monthly (Pro)

On-premises, enterprise collaboration solution for documents, emails, calendars and more.

A fully fledged, free email server solution, an open source project (GPL v2).

Open Source

Internet Information Services is a web server for Microsoft Windows

Boost your productivity with reliable access anywhere with services like email, calendar, file sharing, meetings, instant messaging, and Office Online

Use this program to "Unspam" your mailbox(es).

Open Source

Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.

Say goodbye to phone and email tag for finding the perfect meeting time with Calendly. It's 100% free, super easy to use and you'll love our customer service.

Sharing & communication software for business

Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.

An open source software implementation of the Java Servlet and JavaServer Pages technologies

Open Source

Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.